In conventional impact motors of this type, the hammer piston is guided directly in the drive chamber and in order to ensure the functioning of the impact motor, oil is supplied to the drive air. Not only the oil that is suspended in the drive air in the drive chamber but also a part of the oil that is deposited on the hammer piston and the walls of a drive chamber are drawn out into the atmosphere by the air that exhausts from the drive chamber in each stroke. Of all the oil that in this way continuously leaves the impact motor, the major part is suspended in the air in form of very small particles. This oil dispersed in the air is a very serious hazard to the health of the persons that are in the neighborhood of the impact motor.
It is an object of the invention to solve this problem, and, according to the invention, oil need not be added to the drive air.